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The human oral bacterium Streptococcus gordonii expresses, on the cell surface, two antigenically related high-molecular-mass polypeptides denoted CshA and CshB, encoded by genes at separate chromosomal loci. The precursor form of CshA is composed of four distinct segments: (i) a 41-amino-acid residue leader peptide, (ii) W-terminal 42–878 residues, (iii) residues 879–2417 comprising 13 repeat blocks of 101 amino acid residues and three shorter blocks, and (iv) a C-terminal anchor domain similar to those present in some other Gram-positive bacterial cell-wall polypeptides. Insertional mutations within cshA reduced both cell-surface hydrophobicity and ability to adhere to oral Actinomyces naeslundii. Insertional mutations in cshB had less effect on hydrophobicity and coadherence. However, expression of both polypeptides was found to be necessary for streptococci to colonize the murine oral cavity.

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Background It has been suggested that intestinal microbiota of allergic and non-allergic children differs in composition, and that microbiota–immune system interactions may predispose children to develop sensitization. Previous studies have examined fecal microbiota of allergic children with atopic dermatitis, but little is known about that of atopic wheezy children.Objective To investigate the composition of the fecal microbiota of young sensitized wheezy and non-sensitized non-wheezy children, using molecular methods.Methods Within the context of a prospective birth cohort, we carried out a nested case–control study of sensitized wheezy children (cases) and non-sensitized non-wheezy controls. Cases and controls were matched for age, sex, parental atopy, allergen exposure, and pet ownership. We evaluated the composition of fecal microbiota by nucleic acid-based methods (PCR combined with denaturing gradient gel electrophoresis and quantification of bifidobacteria by fluorescent in situ hybridization).Results Thirty-three case–control pairs (mean age 4.4 years) provided stool samples. Comparison of total bacterial community profiles showed that each child had a unique fecal microbiota (mean Dice's similarity coefficient 22%, range 3.3–60.8%). There was no difference between the groups in prevalence of Lactic Acid bacteria (12/33 vs. 11/33, P=0.8) or bifidobacteria (30/33 vs. 31/33, P=1.00, cases vs. controls). The bifidobacterial species detected were similar in both groups. The percentage of bifidobacteria in total fecal microflora was no different between cases (median 1.7%, range 0–20.8%) and controls (1.9%, 0–18.2%, P=0.7). However, cases with eczema had significantly fewer bifidobacteria (median 1.6%, range 0–4.8%) than their controls (4.0%, 1.9–18.2%, P=0.05).Conclusion We found no differences in fecal microbiota composition between sensitized wheezy and non-sensitized, non-wheezy children aged 3–5 years using nucleic acid-based methods. Differences appear to be isolated to those allergic children with eczema.

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Abstract Mice fed β-2-thienylalanine (β-2-T) by oesophageal tube were no more susceptible to gastrointestinal tract colonization by Salmonella typhimurium or Shigella flexneri III than control mice fed water. In both β-2-T-fed and water-fed groups, the increasing dosage of S. typhimurium, in logarithmic increments to groups of mice, resulted in increasing numbers of these bacteria detectable on dilution plates from organ homogenates. Colonization by S. flexneri III only occurred at a dosage of 108 bacteria for both groups. Pretreatment with 50 mg streptomycin allowed 103 Salmonella or 104 Shigella to colonize both β-2-T- and water-fed groups. Coliforms, inhibited by β-2-T under certain conditions in vitro, were found in equal numbers in both groups. No obvious differences were noted in either types of other bacteria detected or numbers recovered from the two groups. No gross behavioural changes were noted in mice fed β-2-T and not challenged with pathogenic bacteria, and no pathological changes were noted in hepatic or splenic tissues. With increasing Salmonella dosage, collections of polymorpho-nuclear leucocytes, which were almost focal, and increased numbers of giant cells were noted in splenic red pulp areas, in both groups.